The Smart Grid concept for upgrading electrical systems has brought with it the change-out of millions of electricity meters. Older electromechanical meters are being exchanged for newer solid state electricity meters with communication capabilities, and the majority of these new meters include a whole-house disconnect switch mechanism. Many of the electricity meters being replaced have been in service at residential locations for years. An electricity meter installation generally does not get serviced or maintained, so some of the older meter sockets in which those meters were installed may have deteriorated over time. Installation of a new electricity meter into a deteriorated meter socket may create a poor electrical connection even though the meter being installed is in good working order.
Typically, a single-phase ANSI meter has four blades that extend out of a thermoplastic base. These blades insert into spring loaded jaws of a meter socket that is typically mounted on the wall of a residence. In some of the older residential locations, the jaws of the meter socket may have lost the contact force to mate solidly with the meter blades. An installer may not recognize that one or more blades are not making as good contact as desired at time of installation.
Poor electrical connection between the meter and socket can create a situation where an arc can develop within the meter-to-socket interface. There have been occasions where house fires have resulted from a sustained arc condition of this meter-socket type.
Attempts have been made to sense “hot socket” conditions by measurement of blade temperature, socket temperature, or meter temperature. Unfortunately, sensing temperature of these elements during an arc event requires that the arc exist for a sufficiently long time to generate intense heating. There is a possibility that by the time the heat is detected, the arc condition may sufficiently degrade the equipment to create a dangerous situation.
There have also been attempts to solve a related problem using AFCI devices for residential applications. These AFCI devices sense voltage and/or current associated with a load and attempt to develop a “signature” that is associated with an arc condition. The characteristics of the arc are typically sensed by looking at different frequencies of noise that can be present in the voltage and current signals on the power line. If an arc is detected, the AFCI device can open the load current and remove the arc condition if it's on the circuit being monitored. Other attempted solutions for arc detection have involved sensing the light generated by an arc.